SATELLITE PICTURE SHOWING THUNDERSTORM ACTIVITY IN A CONVERGENCE ZONE WEST OF THE NORTH ISLAND

1997 ◽  
Vol 17 (2) ◽  
pp. 33
Author(s):  
Brenstrum
Keyword(s):  
Thunderstorm Activity ◽  
Convergence Zone ◽  
The North

Studies of winds and weather during migrations of Simulium damnosum Theobald (Diptera: Simuliidae), the vector of onchocerciasis in West Africa

1980 ◽  
Vol 70 (4) ◽  
pp. 693-716 ◽  
Author(s):  
J. I. Magor ◽  
L. J. Rosenberg
Keyword(s):  
West Africa ◽  
Time Of Arrival ◽  
Convergence Zone ◽  
Gonotrophic Cycle ◽  
Inter Tropical Convergence Zone ◽  
The North ◽  
Simulium Damnosum ◽  
Host Seeking ◽  
First Time ◽  
High Winds

AbstractReports of the presence and absence of biting by Simulium damnosum Theo. in the Volta River Basin in 1962, 1966 and 1975 were used to identify occasions when sites were invaded by parous and nulliparous females. Circumstantial evidence suggests that this insect is a wind-borne migrant, and the weather before and during some of these invasions was examined. Although most invasions studied took place south of the Inter-tropical Convergence Zone, for the first time evidence is presented suggesting that migration also takes place to the north of this zone. Immigrants were captured at the invaded sites only when light winds or calms were present. This cannot, however, be used as proof that S. damnosum migrates and lands only where winds are light or it is calm because host-seeking is inhibited by high winds and the time of arrival, as opposed to capture on a host, is unknown. Until the factors initiating emigration, as well as the height, duration and number of flights in each gonotrophic cycle and the time of immigration are known, the present findings cannot be tested rigorously nor can wind records be used to trace the source of immigrants.

scholarly journals The Impact of Concave Coastline on Rainfall Offshore Distribution over Indonesian Maritime Continent

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Furqon Alfahmi ◽  
Rizaldi Boer ◽  
Rahmat Hidayat ◽  
Perdinan ◽  
Ardhasena Sopaheluwakan
Keyword(s):  
Rainfall Intensity ◽  
Land Breeze ◽  
Convergence Zone ◽  
Maritime Continent ◽  
Low Level ◽  
The North ◽  
The World ◽  
The Impact ◽  
Support Activity ◽  
Trmm 3B42

Indonesian Maritime Continent has the second longest coastline in the world, but the characteristics of offshore rainfall and its relation to coastline type are not clearly understood. As a region with eighty percent being an ocean, knowledge of offshore rainfall is important to support activity over oceans. This study investigates the climatology of offshore rainfall based on TRMM 3B42 composite during 1998-2015 and its dynamical atmosphere which induces high rainfall intensity using WRF-ARW. The result shows that concave coastline drives the increasing rainfall over ocean with Cenderawasih Bay (widest concave coastline) having the highest rainfall offshore intensity (16.5 mm per day) over Indonesian Maritime Continent. Monthly peak offshore rainfall over concave coastline is related to direction of concave coastline and peak of diurnal cycle influenced by the shifting of low level convergence. Concave coastline facing the north has peak during northwesterly monsoonal flow (March), while concave coastline facing the east has peak during easterly monsoonal flow (July). Low level convergence zone shifts from inland during daytime to ocean during nighttime. Due to shape of concave coastline, land breeze strengthens low level convergence and supports merging rainfall over ocean during nighttime. Rainfall propagating from the area around inland to ocean is approximately 5.4 m/s over Cenderawasih Bay and 4.1 m/s over Tolo Bay. Merger rainfall and low level convergence are playing role in increasing offshore rainfall over concave coastline.

scholarly journals Copepod carcasses in the subtropical convergence zone of the Sargasso Sea: implications for microbial community composition, system respiration and carbon flux

2019 ◽  
Vol 41 (4) ◽  
pp. 549-560 ◽  
Author(s):  
Kam W Tang ◽  
Liv Backhaus ◽  
Lasse Riemann ◽  
Marja Koski ◽  
Hans-Peter Grossart ◽  
...  
Keyword(s):  
North Atlantic ◽  
Carbon Flux ◽  
Cold Water ◽  
Microbial Community Composition ◽  
Convergence Zone ◽  
Sargasso Sea ◽  
The North ◽  
Water Column Stratification ◽  
Vast Area ◽  
Subtropical Convergence Zone

Abstract The oligotrophic subtropical gyre covers a vast area of the Atlantic Ocean. Decades of time-series monitoring have generated detailed temporal information about zooplankton species and abundances at fixed locations within the gyre, but their live/dead status is often omitted, especially in the dynamic subtropical convergence zone (STCZ) where the water column stratification pattern can change considerably across the front as warm and cold water masses converge. We conducted a detailed survey in the North Atlantic STCZ and showed that over 85% of the copepods were typically concentrated in the upper 200 m. Copepod carcasses were present in all samples and their proportional numerical abundances increased with depth, reaching up to 91% at 300–400 m. Overall, 14–19% of the copepods within the upper 200 m were carcasses. Shipboard experiments showed that during carcass decomposition, microbial respiration increased, and the bacterial community associated with the carcasses diverged from that in the ambient water. Combining field and experimental data, we estimated that decomposing copepod carcasses constitute a negligible oxygen sink in the STCZ, but sinking carcasses may represent an overlooked portion of the passive carbon sinking flux and should be incorporated in future studies of carbon flux in this area.

scholarly journals An Intertropical Convergence Zone shift controlled the terrestrial material supply on the Ninetyeast Ridge

2021 ◽  
Author(s):  
Xudong Xu ◽  
Jianguo Liu ◽  
Yun Huang ◽  
Lanlan Zhang ◽  
Liang Yi ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Last Glacial Maximum ◽  
Intertropical Convergence Zone ◽  
Glacial Maximum ◽  
Sediment Supply ◽  
Convergence Zone ◽  
Ninetyeast Ridge ◽  
Last Glacial ◽  
The North ◽  
Terrestrial Material

Abstract. Among various climate drivers, direct evidence for the Intertropical Convergence Zone (ITCZ) control of sediment supply on the millennium scale is lacking, and the changes in ITCZ migration demonstrated in paleoclimate records need to be better investigated. Here, we use clay minerals and Sr-Nd isotopes obtained from a gravity core on the Ninetyeast Ridge to track the corresponding source variations and analyze the relationship between terrestrial material supplementation and climatic changes. On the glacial-interglacial scale, chemical weathering weakened during the North Atlantic cold climate periods, and falling sea level hindered the transport of smectite into the study area due to the exposure of islands. However, the influence of the South Asian monsoon on the sediment supply was not obvious on the millennium scale. We suggest that the north-south migration of the ITCZ controlled the rainfall in Myanmar and further directly determined the supply of clay minerals on the millennium scale because the transport of smectite was highly connected with ITCZ location. Furthermore, the regional shift of the ITCZ induced an abnormal increase in the smectite percentage during the late Last Glacial Maximum (LGM) in our records. The smectite percentage in the studied core is similar to distinct ITCZ records in different time periods, revealing that regional changes in the ITCZ were significantly obvious, and that the ITCZ is not a simple N-S displacement and closer connections occurred between the Northern-Southern Hemispheres in the eastern Indian Ocean during the late Last Glacial Maximum (LGM).

scholarly journals Thunderstorm climatology over Indian region

MAUSAM ◽  
2021 ◽  
Vol 58 (2) ◽  
pp. 189-212
Author(s):  
AJIT TYAGI
Keyword(s):  
West Bengal ◽  
Thunderstorm Activity ◽  
Severe Weather ◽  
Indian Region ◽  
Quality Data ◽  
Full Time ◽  
Climatological Data ◽  
The North ◽  
Annual Frequency ◽  
The Impact

Thunderstorm is a severe weather phenomenon, the impact of which is being increasingly felt by all the sectors of society. In this study attempt has been made to develop thunderstorm climatology over Indian region based on latest representative climatological data. In all, data of 450 observatories comprising of 390 IMD observatories, 50 IAF observatories, six Bangladesh observatories, two Pakistan observatories, and one each in Nepal and Sri Lanka have been analysed. Inclusion of climatological data of Indian Air Force and Bangladesh has helped in developing representative climatology over Indian region. The study has brought out higher (100-120 days) annual frequency of thunderstorm as compared to those given by earlier studies (80-100 days). The highest annual frequency (100-120 days) is observed over Assam and Sub Himalayan West Bengal in the east and Jammu region in the north. The lowest frequency (less than 5 days) is observed over Ladakh region. In the plains Gangetic West Bengal and Bangladesh record between 80 and 100 days of thunderstorm annually. Kerala records highest (80-100 days) thunderstorm frequency of thunderstorm over peninsula. Udhampur observatory (132 days) in Jammu sub-division records highest number of thunderstorms in the country followed by Kumbhigram (Silchar) observatory (129 days) in south Assam and Hasimara (123 days) in Sub Himalayan West Bengal. In the plains Saurashtra and Kutch record lowest number (less than 15 days) of thunderstorm in the country. Thunderstorms are primarily short lived mesoscale weather phenomena. Existing synoptic network of part time observatories have limitations in recording all the occurrences of thunderstorms at the observatory and adjoining areas. Inclusion of data from such observatories results in lower frequency of the event and vitiates climatology. Efforts have been made in this study to develop thunderstorm climatology by using quality data of full time current weather (Airport) observatories, class I and selected class II IMD observatories. Since number of full time observatories in most of the sub divisions is few, the study is not able to bring out finer spatial variation of thunderstorm activity with in sub-divisions. Thunderstorm is a high impact severe weather event, which affects all the sectors of the society. Therefore, both from operational and climatological point of view, there is urgent need to establish at least one full time current weather observatory in each district to ensure proper reporting of all thunderstorm occurrences and to build district level thunderstorm climatology in the country.

scholarly journals Study of thunderstorm activity in Volyn Region and in Ukraine using the data of Blitzortung online resource

2021 ◽  
pp. 16-28
Author(s):  
V. V. Fedoniuk ◽  
M. A. Fedoniuk ◽  
A. M. Pavlus
Keyword(s):  
Regional Analysis ◽  
Graphical Analysis ◽  
Thunderstorm Activity ◽  
The West ◽  
Storm Activity ◽  
The North ◽  
Regional Features ◽  
Online Resource ◽  
Climatic Normal ◽  
Activity Dynamics

The article contains the results of statistical and graphical analysis of thunderstorm activity in Ukraine and within Volyn Region, in particular, following the study of the dynamic maps archive available at the online resource Blitzortung.org (lightnings and thunderstorms in real time). It describes the principles and results of activities of Blitzortung.org, a community of lightning direction sensors owners and users, and presents the developed algorithm of the methodology of reading dynamic maps available at this resource. Regional analysis of the archival maps on the website Blitzortung.org for 2008-2019 for the territory of Volyn Region made it possible to establish the following changes of the thunderstorm activity dynamics: the total number of thunderstorm days more than doubled (from 30 to 68.3 days on average); the number of thunderstorms increased in April (it was a rare phenomenon earlier); the number of thunderstorms increased significantly in May, for some years the number of thunderstorm days in May reached certain summer months (June and July); most thunderstorms are of frontal origin, storm fronts come from the west, north and southwest. The number of frontal thunderstorms tends to increase, therefore indicating increased atmospheric instability and the number of natural meteorological phenomena associated with such instability; the average monthly number of thunderstorm days in Volyn Region also increased for all months of the year with no exception. The analysis of storm activity within the whole territory of Ukraine during the period of 2018-2019 indicated the presence of clear regional features and differences. The increase in thunderstorm activity is observed in the western (50-100%) and southern (15-50%) regions of the country, and partly in the north. The number of thunderstorm days in the eastern part of Ukraine is close to the climatic normal. At the same time, the analysis needs to be clarified and detailed throughout the whole network of meteorological stations of Ukraine whose data can be compared with the results of the study of archival maps available at Blitzortung.org.

Role of the climatological intertropical convergence zone in the seasonal footprinting mechanism of the El Niño-Southern Oscillation

2021 ◽  
pp. 1-43
Author(s):  
Jae-Heung Park ◽  
Mi-Kyung Sung ◽  
Young-Min Yang ◽  
Jiuwei Zhao ◽  
Soon-Il An ◽  
...  
Keyword(s):  
North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
The North ◽  
The Pacific ◽  
The North Pacific ◽  
Northern Branch ◽  
Mean State

AbstractThe North Pacific Oscillation (NPO), a primary atmospheric mode over the North Pacific in boreal winter, is known to trigger the El Niño-Southern Oscillation (ENSO) in the following winter, the process of which is recognized as the seasonal footprinting mechanism (SFM). Based on the analysis of model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we found that the SFM acts differently among models, and the correlation between the NPO and subsequent ENSO events, called the SFM efficiency, depends on the background mean state of the model. That is, SFM efficiency becomes stronger as the climatological position of the Pacific Intertropical Convergence Zone (ITCZ) moves poleward, representing an intensification of the northern branch of the ITCZ. When the Pacific ITCZ is located poleward, the wind-evaporation-sea surface temperature (SST) feedback becomes stronger as the precipitation response to the SST anomaly is stronger in higher latitudes compared to that of lower latitudes. In addition, such active ocean-atmosphere interactions enhance NPO variability, favoring the SFM to operate efficiently and trigger an ENSO event. Consistent with the model results, the observed SFM efficiency increased during the decades in which the northern branch of the climatological ITCZ was intensified, supporting the importance of the tropical mean state of precipitation around the Pacific ITCZ.

scholarly journals Convergence zone propagation in the North American Basin

1974 ◽  
Vol 55 (S1) ◽  
pp. S57-S57
Author(s):  
J. D. Shaffer ◽  
A. N. Guthrie ◽  
R. M. Fitzgerald ◽  
D. A. Nutile
Keyword(s):  
North American ◽  
Convergence Zone ◽  
The North ◽  
American Basin
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